1. Field of the Invention
The present invention relates to an antenna structure, particularly to a structure of a miniature antenna applying to wireless communication products.
2. Description of the Related Art
Portable electronic products, such as mobile phones, WLAN (Wireless Local Area Network) products and GPS (Global Positioning System) products have flourished due to rapid advance of wireless communication technology. Because of market competition and consumers' desire for high-end products, the related manufacturers not only lay emphasis on electronic performance but also pay much attention to design appearance. Thus, the antennae, which are originally externally exposed, have gradually become internally designed. The concealed antennae, though arranged in a small confined space, still have to maintain a superior capability of signal receiving and transmitting.
Two of the commonly concealed antennae are the monopole antenna and the Planar Inverted F Antenna (PIFA). The monopole antenna is inexpensive with a simple structure. Length of the monopole antenna, however, cannot be effectively reduced due to the requirement of signal receiving efficiency. Therefore, use of the monopole antenna may impair the appearance of portable electronic products and has gradually become obsolete. PIFA, with a wider operation bandwidth, can be adapted to the form of a portable electronic device. Thus, PIFA is more widely used on the market. Both the monopole and the PIFA antennae are prone to be affected by the reactance effect generated due to the presence of dielectric materials or human body in the near-field region. This may result in frequency shift of the antenna. In other words, any object that is near to the antenna may affect its performance, causing a decrease of its efficiency of signal transmitting/receiving and an increase in noise.
Accordingly, the present invention proposes a miniature antenna characterized in a small size and a capability of confining induced current to the proximity of the antenna to overcome the conventional problems.